PiN or NiP diodes are frequently used in RF applications as RF switches. PiN/NiP diodes have the characteristic that their conduction can be changed by applying appropriate bias voltage. When used as a switch, the diode can be turned ‘OFF’ by applying a reverse bias voltage across it that is of sufficient amplitude to prevent the RF signal from passing through the diode. Similarly, a forward bias can be applied across the diode to turn it ‘ON’ and make it conduct. The current generated by the forward bias determines the amount of conduction allowed. Since the reverse bias has to be of sufficient amplitude to block an RF signal, the reverse bias voltage is usually a high voltage, whereas the forward bias voltage is a low voltage.
For a typical PiN/NiP diode, the driver circuit for the bias voltage must be able to switch from reverse bias to forward bias in order to turn the PiN/NiP diode ‘ON’. There are several methods of driving the PiN/NiP diodes, which generally include the use of mechanical relays, MOSFETs, IGBTs, and the like, to alternatively apply one of the reverse bias and the forward bias to the PiN/NiP diode. For example in a driver circuit that uses MOSFETs, one for each of the reverse bias and the forward bias, the MOSFETs may be switched ‘on’ or ‘off’ by applying voltage between their respective gate and source connections. When the high voltage side MOSFET turns ‘on’, the source connection of this MOSFET needs to go to the high voltage potential. To keep the high voltage side MOSFET turned ‘on’, the gate of this MOSFET must go to a potential higher than the high voltage potential of the source plus the gate threshold voltage. This condition of maintaining the high voltage MOSFET turned ‘on’ requires the circuit driving the gate to float above the source, which can be a problem since it necessitates the use of complex circuitry to drive the high voltage side MOSFET.
Gate driver circuits become even more complex when used as part of PiN/NiP diode driver circuitry, in uses when the PiN/NiP diode needs to be turned ‘ON’ or ‘OFF’ for a considerable duration. Typically, gate driver circuits are designed for high frequency, high speed switching applications, where the MOSFETs are being switched at frequencies typically in the kHz range. When such circuits are used to drive PiN/NiP diodes, specialized circuitry must be used to enable their use for low frequency switching. For these reasons, PiN/NiP driver circuits are generally complex and expensive, and less complex and expensive PiN/NiP driver circuits are desirable. The same is true for other high voltage switching applications in which high speed switching is desirable alongside low frequency switching.